Plant secondary metabolism is rich in compounds (i.e. phytochemicals) with promising (bio)activities or functionalities. These (bio)active phytochemicals can be exploited for the benefit of human/animal/plant health. For example, the rich stereochemical and functional group diversity of phytochemicals offers a wide range of functionalities with respect to inhibition of unwanted microorganisms and novel alternatives to traditional antimicrobials.
The Plant (Bio)Actives group currently focusses on promising antimicrobial phytochemicals. To obtain these antimicrobials we use two main strategies: induction in-planta using diverse (a)biotic elicitors and valorization from agri-food by-products. Using our core analytical expertise (in close collaboration with the FCH Phytochemical research group) we chemically characterize and purify candidate compounds for antimicrobial activity characterization.
Description of theme
The work of the Plant (Bio)Actives group is characterized by being at the interface of (phyto)chemistry, microbiology and (in-silico) molecular modelling. More specifically, our aim is to (i) characterize the antimicrobial properties/functionalities of phytochemicals and find synergistic combinations; (ii) predict and rationalize their (quantitative) structure-activity relationships; and (iii) elucidate their mode of action (MoA). At Plant (Bio)Actives, in-silico modelling is coupled with in-vitro evidence to rationalize and predict the properties and MoA of antimicrobial phytochemicals.
1) Antimicrobial properties and synergistic combinations
Phytochemicals have been shown to be effective antimicrobials against bacteria (cells and spores), fungi and viruses. An interesting strategy to control microorganisms is to design combinations of multi-targeted antimicrobials, just like plants do when exposed to pathogens. To create effective synergistic combinations, it is necessary to first characterize the different functionalities that different families of phytochemicals have (e.g. inhibition of specific proteins, damage of bacterial membrane, efflux pump inhibition, oxidative stress). Quantification of their activity and mapping their spectrum of activity is an essential part of this research. By using synergistic combinations of plant antimicrobials (i) the potency of the antimicrobial cocktail is increased; (ii) the dosage can be reduced, making the approach more feasible to be applied in e.g. foods; and (iii) the risk of persistent or resistant cells survival is significantly reduced.
2) Structure-activity relationships (SAR)
The activity of phytochemicals is strongly linked to their structure. Rather subtle structural differences can lead to a substantial change in the antimicrobial properties. Quantitative SAR analysis is a chemometric tool that allows to (i) perform a predictive assessment for an efficient discovery and isolation of antimicrobial phytochemicals (e.g. limit the number of purification experiments or save purified compounds); (ii) speed up the design and optimization of lead antimicrobial scaffolds; (iii) provide insights into the molecular properties important for activity. A well-balanced approach using both a predictive assessment and in-vitro screening is necessary to guide this research.
3) Mode of action
To apply plant-derived antimicrobials in e.g. food, feed or environment, their molecular mechanisms should be well-defined and validated. Elucidation of the molecular targets of antimicrobial phytochemicals using in-vitro assays is coupled with in-silico tools. In-vitro assays include cell-based (fluorescence) assays, MS-based targeted analysis, and -omics profiling (in collaboration with other research groups). In-silico tools include calculation of molecular properties, 3D pharmacophore modelling and molecular docking.
- Antimicrobial isothiocyanates from Brassicaceae glucosinolates: Analysis, reactivity, and quantitative structure-activity relationships (finalized 2020), Dr. Silvia Andini, Prof. Dr. Ir. Jean-Paul Vincken, Dr. Carla Araya-Cloutier
- Prenylated (iso)flavonoids as antimicrobial agents: Production, activity and mode of action (finalized 2021), Dr. Sylvia Kalli, Prof. Dr. Ir. Jean-Paul Vincken, Dr. Carla Araya-Cloutier
- Valorization of licorice root by-product for safe, natural antimicrobials (with WUR Human Nutrition), Sarah van Dinteren (MSc), Prof. Dr. Ir. Jean-Paul Vincken, Dr. Carla Araya-Cloutier, Dr. Jocelijn Meijerink
- Phytochemicals as efflux pump inhibitors in bacteria, Marina Ika Irianti (MSc), Prof. Dr. Ir. Jean-Paul Vincken, Dr. Carla Araya-Cloutier
- Mechanism of action of antibacterial phytochemicals against Listeria monocytogenes (with WUR Food Microbiology), Alberto Bombelli (MSc), Dr.Ir. Heidy den Besten, Dr. Carla Araya-Cloutier
- Mechanism of action and cytotoxicity of prenylated phenolic compounds (with WUR Toxicology), Janniek Ritsema (MSc), Prof. Dr. Ir. Jean-Paul Vincken, Dr. Carla Araya-Cloutier, Dr. Nynke Kramer